The present invention relates to a support pad/guide bar, which is intended to be mounted in a seat on the cutter head of a deep hole drill, said support pad/guide bar having a longitudinal direction and a cross-direction, and that the support pad/guide bar has, at least one contact surface, on the side thereof turned outwards in the mounted state, which is intended to cooperate with the hole wall. The two most common systems in deep hole drilling are presently the STS (Single Tube System) system and the Ejector system, at which the support pad/guide bar according to the present invention may be used in connection with a deep hole drill which relates to both these systems.
In deep hole drilling in a workpiece, a commonly occurring problem is that the support pads and guide bars, which are arranged on the cutter head, are subjected to the formation of crack during the deep hole drilling. The reason for this is that the support pads/guide bars are normally made of solid cemented carbide, whereby said support pads/guide bars may be exchangeably fixed on the cutter head or in various ways connected by soldering to the cutter head. During the drilling process, the support pads/guide bars are exposed to high temperatures by the fact that the friction against the hole wall may be high. However, most often so that the entire support pad/guide bar does not abut against the hole wall, and therefore only a part of said support pad/guide bar is exposed to said friction. The cooling liquid flowing between the cutter head and the bore hole will not be in contact with the support pad/guide bar in the areas where abutment takes place between the support pad/guide bar and the hole wall to a sufficient extent. As a consequence of these interacting circumstances, i.e. high friction and deficient cooling, cracks arise in the support pads/guide bars, which reduces the service life of said support pads/guide bars.
The present invention has as its aim the definition of a support pad/guide bar of the kind defined in the introduction, which is so designed that a substantially improved cooling of the support pad/guide bar is achieved. Another aim of the present invention is to increase the service life of the support pad/guide bar by reducing the occurrence of cracks in the support pad/guide bar.
The aims of the invention are realized by means of an element, i.e., a support pad or a guide bar, which is adapted to be mounted in a seat of a cutter head of a deep hole drill. The element comprises a body which defines a longitudinal direction and a cross-direction. The body includes an inner mounting side and an opposing outer side. The outer side includes a contact surface adapted to engage a wall of a hole being drilled. The outer side also includes a countersink which extends across the outer side in a direction transversely of the longitudinal direction, wherein an edge of the contact surface facing toward a center of the body forms an angle with the longitudinal direction in the range of 55 plus or minus 100xc2x0.